I had a 2005 5.3 and you had to baby it to get 18 mpg. My 2018 will get 24 if you do that same drill. GM did it by improving efficiency and power by raising compression... along with variable timing and combustion chamber improvements. They also went from iron to al on the blocks which dropped a little weight.
My 2017 2.7 Ferd got 23.5 mpg. The ford has a little lower compression ratio.. four times the cams, two turbos and a lot of single points of failure that the GM does not have... The ford is AL and a little taller in the wind..
There is still plenty of life left in the basic architecture of theV6/8. Batteries and emissions will get it... unless an achates engine comes out of left field.

This is 6k miles with QS ultimate durability... if you see my pic, there is hardly any metal... and very small minute particles. Engine has 7k on it.
The 5.3 is a V8 and you are going to have some metal.... bigger pieces = bigger problems.
another item i might check is the "sound" that is, you can do some vibration analysis and tell from the frequency.. like is the noise half the rpm, a quarter and so and figure out what the source is.. like a crank, a lifter, or a cam. the iphone app is named vibration analysis.
good luck.

On the marked roller and mating surface of the camshaft... I recommend that you install a drain plug with a good magnet. If the hardened surface of the cam starts to fail on that lobe.. some of the remnants will end up on your magnet. Each time you drain, you will be able to see if any of the iron hardened parts are starting to shell.. You can get fancy and weigh it after each change and track it. In my experience, though, you will look at it and know when something is flying apart inside.

This is my second 5.3
My first was an iron block 5.3 2005 in a Yukon. I was moving addresses, it started raining, which got me stepping on it.. That yukon was moving at 90 mph with a 18 ft trailer with 5000 lbs on it.. effortlessly.
I have a 2018 5.3 with a diablo V4 M5 AFM blocker. They are sweet engines at this point, and sooner or later we will be at $4 gas again.
Just changed the oil.. 153 hours and not enough metal to measure. You can see on my finger.. that what metal is there is very tiny.. no large or heavy chunks.. like i have seen from other engines.. these 5.3 will go a long way if you keep the dirt of them and keep the oil clean.
IMG_0817.HEIC

I have helped my dad get his house "off the grid" and my thoughts after that deal.. is that he has a 40KWH battery if the weather is warm. I think you are much better off to take a stationary object and perfect energy self sufficiency with heavy cheap batteries than to impose the weight issue you need to on a vehicle and have rare element batteries. I think using the fossil fuels for transportation makes more sense. And CNG would be a great way to go as well.
==Pete

I had the F150 a 2017 Lariat 4x4 Eco 2.7
It was in the shop for 29 days replacing 4 oil pans and one blown radiator. And i babied the truck.. No telling how the 2.7 would hold up if it was towing something.. I don't think you can use tupperware oil pans in Tex/Ok areas.. ambient temps are just too hot for turbo charged engines.. in 108 deg heat.
Blown radiator was probably a head gasket leak. Ford only replaced the radiator. 35600 miles. Owning the Ford cost me $9k.Bought a new 2018 GMC $13k off sticker. More solid, more industrial. Better cabin, better radio and gadget capability. And a V8 with a die cast aluminum oil pan.
No leaks.
Still have the Ford oil spill in a 6 ft oval on my garage floor where i park. No more Fords for me...

I recommend changing the rear differential as soon as possible. i bought a December 18 built 2018 in march. The rear had a thin gray lubricant in it. I have not seen a hypoid gear oil that looked like it at all. Replaced with 75-90 Mobil1. If you really want to be bullet proof, i have used SHC 535 in my Jeep T90 and D18. Not a consumer lube, but you have to buy it to appreciate it. That oil is rated at like 10,000 hours.
Do this, especially if you plan to tow. Towing increases the temperature in the rear differential to temps like 200 degrees...

My dad has had three RAMs, 13 gas 3.6, 15 eco and 18 gas 3.6.I drive it quite often, the longest run from OKC to South Jersey. Ram #1 dropped a tranny, but otherwise solid.The eco was a toad to drive and $$$ for maintaining. The 18 is sweet. I do think the 3.6 is the better engine. It's sister is the 3.5 mercedes. Not too sure about the long term MDS on the hemi.
As far as ford, they don't all burn oil. My 17 2.7 eco leaked oil. Four oil pans (they are tupperware like plastic) and i went to a december built GMC SLT 18 with a die cast aluminum oil pan and no turbos.
I think the ford has the best ad campaign.. the best handling truck, but stay away from the turbos. I also blew a radiator apart... on my 2.7.
The GM is solid, more an industrial vehicle than the ford. I would not buy another Ford... 29 days in the shop in less than two years. How GM got the 5.3 to do as well as it does on the hwy mileage is astounding. Mine has a 3.08 ring gear, and always punches above 20 mpg. So far the only demerit on the GMC has been the fill on the rear. GM saved way too much on the lube, and i saved it to remind me how we can be pennywise but pound foolish on a truck that was $56k and i paid $39k. GM.. RAMS... then Ford if you have to.

The alternator is rated over 100 amps.. That would require a #1 AWG wire at least.. i think that the connector looks a little light for continuous 140 Amps of current... and the insulation is also a little weak for continuous current and the heating. I hate to see crimped connectors on large wire like this. its a lot better to have fargo type compression connector. Wire gets hot and cold and sooner or later works itself loose from the needed tightness to carry the current without heating...
You can do better with parallel conductors, smaller wire, but two runs... solder the terminal ends.
This is a critical area when you have a truck full of sensors and computers... Yikes.

This is my second GMC in the last 15 years or so... Just traded a '17 F150 with the eco 2.7 and three oil pan changes and a blown radiator. I have had a lot of trucks/autos/suvs and never had one that took four plastic oil pans. Ford has a real problem with quality. My 5.3 has die cast aluminum oil pan and no water cooled turbos. The ford has some good points, like the handling compared to the GMC. My F150 was in the shop 28 days. There is just no way around that problem. I am not so hot on the chevy look, but i do think the GMC is as sharp as the 150. The inside of the GMC is better, i mean mine has a weather radar feature, a gadget to be sure, but one i like.
I also tend to think the 5.3 will way outlast the 2.7. Maybe twice as long.

4400 miles. 2018 December build. I did have to change the rear differential lube. I believe it was contaminated. Coming from a FERD, so not really a nitpicker yet... AFM disabler... pretty happy with it...